Evaluation of low-fusing porcelain bonded to dental cast Ti–Zr alloys

This study was designed to evaluate the bonding characteristics of titanium porcelain Duceratin bonded to Ti–Zr alloys and commercially pure titanium (c.p. Ti). In addition, the thermal expansion coefficient (CTE) of all Ti–Zr alloys and c.p. Ti was also evaluated. The experimental metals used for this study include c.p. Ti, Ti–10Zr, Ti–20Zr, Ti–30Zr and Ti–40Zr alloys (in wt.%). Experimental results indicated that Ti–10Zr alloy had the highest bond strength and higher than that of c.p. Ti (21.1 MPa). When the Zr content was increased to 20 wt.% or higher, the strengths were below the lower limit value in the DIN 13.927 standard (25 MPa). In addition, the CTE values of the Ti–Zr alloys were lower than that of c.p. Ti (10.1 × 10−6 °C−1), and ranged from 9.9 to 9.4 × 10−6 °C−1. The CTE values had a tendency to decrease as the zirconium content increased. On the other hand, CTEs for Ti–30Zr and Ti–40Zr were below that of Duceratin, and thus, the surfaces of the Ti–30Zr and Ti–40Zr alloy specimens on which the porcelain was fired were seen to curve slightly toward the porcelain side upon cooling. It was concluded that the high bond strength of Ti–10Zr alloy was the result of the low difference in the CTE between this alloy and Duceratin porcelain, which would verify the fact that weak bond strength is the result of a mismatch between CTEs.